CN1754305A - Phase Lead Angle Optimization in Brushless Motor Control - Google Patents

Abstract

A multiphase permanent magnet motor control system is disclosed having a controller that generates control signals that energize each phase winding. The controller includes a current value calculator and a phase lead optimization circuit. Wherein the current value calculator is used for determining a phase current value which is advanced by a phase advance angle of the back electromotive force on the phase; the phase advance optimization circuit is used to generate an optimized phase advance angle value that maximizes motor output torque and minimizes phase current. The phase advance optimization circuit determines an optimized phase advance angle for each phase of the motor.

Description

Phase Lead Angle Optimization in Brushless Motor Control

related application

The subject matter of this application is related to the following pending U.S. application numbers: 09/826423 filed April 5, 2001 by Maslov et al., 09 filed April 5, 2001 by Maslov et al. /826422, 09/966102 filed on October 1, 2001 by Maslov et al., 09/993596 filed on November 27, 2001 by Pyntikov et al., 10/173610 filed on June 19, 2002 by Maslov et al. All batch application numbers belong to this application in common. The disclosures of these applications are incorporated herein by reference.

technical field

The present invention relates to rotating electric machines, and more particularly, to a method for optimizing a phase lead angle for controlling a brushless permanent magnet electric machine.

Background technique

The pending application mentioned above describes the challenges of developing efficient motor drives. Electronically controlled pulsed excitation of motor windings offers the prospect of more flexible management of motor characteristics. Functional diversity is achieved by controlling the width of the pulses, the duty cycle, and applying switching of battery power to the appropriate stator windings. The use of permanent magnets accompanying the windings is advantageous for limiting current losses.

In a vehicle drive environment, it is extremely desirable to be able to achieve smooth operation over a wide range while maintaining the high torque output capability of the motor with minimal functionality. The motor structures described in the pending patent application all address these goals. The electromagnet core segments are configured as annular isolated permeable structures, thereby providing increased magnetic flux density. Isolating the solenoid core segments allows a single solenoid core to create a single flux density on the magnetic core with little flux loss or detrimental mutual inductance effects due to interactions with other electromagnets. caused by mutual inductance between them.

Precise control performance in brushless motor applications involves incorporating non-linear feed-forward compensation coupled with current feedback components. However, the feed-forward compensation expression usually has a large dependence on various circuit parameters, such as phase resistance, phase self-inductance, etc., which are described by the equivalent circuit diagram of a single motor phase illustrated in Figure 1. V _i (t) represents the voltage input of each phase, R _i represents the winding resistance of each phase, and _Li represents the self-inductance of each phase. E _i (t) represents the back EMF voltage applied to each phase of the motor, which can be approximated by the following expression,

E _i (t)＝(K _ei ω)sin(N _r θ _i )

Here K _ei represents the back electromotive force coefficient of each phase, ω(t) represents the rotor speed, Nr represents the logarithm of the permanent magnet, θ _i (t) represents the relative displacement between the ith phase winding and the rotor reference position.

The voltage V _i (t) can be defined by the following equation:

$V_i\left(t\right)={\mathrm{E.}}_i\left(t\right)+R_i{I}_i\left(t\right)+L_i\frac{d}{\mathrm{dt}}{I}_i\left(t\right)$ i=1, 2,... N _s

here

V _i (t) is the winding voltage;

I _i (t) is the phase current;

R _i is the winding resistance;

E _i (t) is the back electromotive force;

L _i is the winding self-inductance;

N _s is the number of stator phase windings.

The voltage V _i (t) is provided by a regulated DC power supply with limited voltage. Since the back EMF is proportional to the motor speed, there is an extreme value of the phase current I _i (t) when the speed is greater than a certain value.

Assumption: The magnetic flux in the air gap is distributed according to a sinusoidal curve, and the steady-state characteristics of back electromotive force and phase current can be defined by the following expressions:

E _i (t)＝E _i sin(θ _i (t))＝K _ei ωsin(N _r ωt+Δ _i )

I _i (t) = I _i sin (θ _i (t)) = I _i sin (N _r ωt + Δ _i ) i = 1, 2, ... N _s

The average total torque is

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; \&tau;i</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

here,

N _r is the number of permanent magnet pole pairs;

K _ei is the back electromotive force coefficient;

Ω is the motor speed;

_Δi is the compensation angle according to the motor geometry;

T is the average total torque output;

K _τi is the torque coefficient.

Therefore, the torque output is also limited by the power supply. A phase lead control technique has been used to widen the operating speed range limited by the maximum supply voltage. Make the phase angle of the armature current lead the back electromotive force instead of forming a sinusoidal armature current (or phase current) in phase with the back electromotive force.

For example, US Patent 6,373,211 to Henry et al. describes a method of widening the operating speed range of a sinusoidally excited permanent magnet motor. This method utilizes the phase advance technology to realize the widening of the operating speed range and reduce the phase current. The extended speed range is provided by controlling the phase lead angle α between the current vector and the back EMF vector. A set of precomputed tables is used to store different torque values at different speeds. The current phase lead angle is calculated from the torque command and the measured speed.

However, the technique proposed by Henry et al. does not provide an optimized value of the phase lead angle to obtain the maximum torque output with the minimum phase current. Instead, the patent discloses setting the maximum output torque T _max . Thus, the speed ω and the required or demanded torque T _cmd are read out. When the speed is equal to ω, if the required torque T _max is larger than the maximum torque that can be obtained, then the required torque T _max is reduced. The phase advance angle can be calculated to obtain a value for the reduced demanded torque T _cmd . Therefore, in the case of reducing the phase current, the phase advance technology adopted in the prior art can provide a phase advance angle for widening the operating speed. However, prior art does not teach optimization of phase lead angle and phase current magnitude to minimize power loss.

In a vehicular drive environment, where available power is limited to the in-vehicle power supply, high torque output capability with minimal power dissipation is extremely desirable. The motor structures described in the pending patent application all address these goals. As described in these applications, electromagnet core segments are configured as annular, isolated permeable structures, thereby providing increased magnetic flux density. Magnetic isolation between the electromagnet core segments allows a single flux density on the magnetic core with little flux loss or detrimental mutual inductance effects due to mutual inductance with other electromagnets caused.

Therefore, it is necessary to optimize the phase advance so that the motor can deliver higher torque output with minimum power consumption.

Furthermore, common phase advance techniques do not provide a method for phase optimization of each phase in a multi-phase motor. However, due to phenomena caused by mechanical/processing errors and other structural features, the phases of each motor will exhibit values within a range for each circuit element. Factors that can affect the value of a circuit parameter include: net flux linkage of the electromagnet core, fluctuations in core inductance relative to the circuit, changes in phase winding resistance due to manufacturing errors such as cross-section, winding tension, etc. Conductivity (related to material grade and material processing, completion history), phase winding process (uniform winding or random winding) or construction quality of each stator coil, insertion position of electromagnet and permanent magnet (that is, the permeability of the magnetic circuit ), the difference in flux density in the air gap, which depends on the permanent magnet rotor magnet assembly, the residual flux density, the bias field due to the external magnetic field, the coil shape (rectangular, circular, or helical), the winding to which the coil reaches The machining error achieved by parameters, core geometry, the core geometry can change the cross-sectional error of the core, the effective length of the winding coil.

Typically, motor control strategies assume uniform parameter values for the entire motor. Use a median parameter to represent all corresponding circuit elements in the motor. The method using lumped parameters often leads to the degradation of tracking performance because the mismatch of parameter values in each phase compensation procedure causes overcompensation or undercompensation of the control strategy. These assumed parameters tend to yield larger deviations for stator structures configured as separate ferromagnetic isolated core components.

Therefore, there is a demand for phase advance optimization technology, which requires the phase advance technology to propose the optimal phase advance angle and the optimal phase current amplitude, so that the motor can output the maximum torque with the minimum power consumption, and consider the individual phase windings and stators Parameter variability in phase component structures.

Contents of the invention

The present invention satisfies this need while retaining the advantages of a separate and ferromagnetically isolated single stator core component construction, such as disclosed in the pending application. The invention can realize the optimization strategy of the phase lead angle to maximize the output torque and minimize the phase current of each phase circuit element. Torque provides an optimal torque control strategy with high precision control capability. In part, this capability is achieved by building a controller in a multiphase permanent magnet motor control system that generates control signals that excite the phase windings, which include a current value calculator and a phase The advanced optimization circuit, in which the current value calculator is used to determine the phase current value of a phase advanced angle relative to the back electromotive force; the phase advanced optimization circuit is used to generate the value of the optimized phase advanced angle, so that the motor output can rotate The torque is the largest and the phase current is the smallest.

Phase-dependent parameters include winding reactance, torque coefficient, phase-dependent back EMF associated with each phase, from which phase lead optimization can be performed on each phase of the motor to account for different winding and stator Parameter variability of phase component structures. The controller can operate in an integrated implementation in which each generated control voltage output is replaced with specific phase parameters. Alternatively, the controller can provide a separate control loop for each stator phase. The loop structure of each phase utilizes the optimum phase lead angle corresponding to a particular phase to generate control signals for the respective phase windings.

The phase advance optimization circuit includes a first optimization section and a second optimization section, the first optimization section is used to determine the maximum torque value at a given speed, the second optimization section responds to the maximum torque value, and generates the optimum phase advance angle value and the optimum magnitude of the phase current. For a given speed and user requested torque, the second optimization part minimizes the phase current.

According to the method in the present invention, the multi-phase permanent magnet motor can be provided with real-time and continuous control by performing the following steps:

Input a torque command signal representing the required torque;

Determine the phase currents required to obtain the desired torque;

In order to obtain the required torque, the control voltage required to excite each phase winding is determined according to the phase current;

If the required control voltage exceeds the power supply voltage, then the phase current is advanced by a phase lead angle relative to the back electromotive force in phase;

According to the required torque, determine the optimized phase lead angle to maximize the output torque of the motor and minimize the phase current;

The optimal phase lead angle can be determined using a lookup table corresponding to the desired torque and motor speed;

The motor control method in the present invention provides favorable conditions for motors of various structures, and this motor control method can be applied in motors in which the stator phase components are composed of ferromagnetically isolated stator electromagnets, Solenoid core parts are formed from individual phase windings, separated from each other and not in direct contact.

The invention is particularly advantageous in motor tracking user initiated variable input applications, such as in electric vehicle tracking control operations. In response to the torque command input signal, the controller selects a desired current trajectory for each phase based on an expression including parameters specific to each phase.

Other advantages of the invention will become apparent to those skilled in the art from the following detailed description, by way of example only of the best contemplated modes of carrying out the invention, wherein the invention shows and describes only one best mode . It should be understood that the present invention also has other different implementations, and details in various implementations can be modified in various obvious ways without departing from the present invention. Accordingly, the drawings and description are intended to be illustrative of the substance and not restrictive.

Description of drawings

The present invention is illustrated by way of example, but not limitation, in which like reference numerals denote like elements in the accompanying drawings, wherein:

Figure 1 is an equivalent circuit diagram of a single phase of the motor;

Fig. 2 is a block diagram of a motor control system according to the present invention;

Figure 3 is a partial circuit diagram of a switching device and driver for a single stator core segment winding of a motor controlled by the system of Figure 2;

Fig. 4 is a three-dimensional sectional view of a motor structure suitable for the control system of Fig. 2;

Fig. 5 is a graph showing torque-speed characteristics under two conditions with and without a phase lead angle;

Figure 6 is a circular diagram illustrating the phase advance technique according to the present invention;

Figure 7 is a block diagram illustrating the torque controller method applied in the control system of Figure 2;

Fig. 8 is a block diagram showing the phase lead angle optimization unit in Fig. 7;

Fig. 9 and Fig. 10 are charts, and it has shown the phase leading angle optimization that the first optimization part performs in Fig. 8;

11 and FIG. 12 are graphs showing the phase lead angle optimization performed by the second optimization part of FIG. 8;

FIG. 13 is a partial block diagram showing the differences in the controller approach in FIG. 7 .

Detailed ways

FIG. 2 is a block diagram of a motor control system according to the present invention. The multiphase electric machine 10 includes a rotor 20 and a stator 30 . The stator has a plurality of phase windings which are switchably energized by a drive current applied by a DC power supply 40 via an electronic switching device 42 . The switching device is connected to a controller 44 via a gate driver 46 . Controller 44 has one or more user inputs, and a plurality of inputs corresponding to motor conditions detected during operation. The current in each phase winding is sensed by a respective one of a plurality of current sensors 48 , the outputs of which are provided to the controller 44 . For this purpose, the controller may have multiple inputs, or alternatively, the signals from the current sensors may be multiplexed and connected to a single controller input. A rotor position sensor 47 is connected to another input of the controller 44 to provide a position signal. The output of the position sensor is also provided to a speed approximator 50 which converts the position signal into a speed signal which is provided to another input of the controller 44 .

The sequence controller may include a microprocessor or equivalent microcontroller, such as Texas Instrument's digital signal processor TMS320LF2407APG. The switching device may consist of multiple MOSFET half-bridges, such as the International Rectifier IRFIZ48N-ND. The gate driver can include the Intersil MOSFET gate driver HIP4082IB. The position sensor may comprise any known sensing device such as Hall effect devices (AllegroMirosystems 92B5308), giant magnetoresistance (GMR) sensors, capacitive rotary sensors, reed switches, pulse coil sensors including amorphous sensors, resolvers, optical sensors and similar sensors. A Hall effect sensor, such as a F.W. Bell SM-15, may be used as the current sensor 48 . The velocity detector 50 may provide an approximation of the time derivative of the measured angular position signal.

Figure 3 is a partial circuit diagram of the switching device and winding driver for a single stator core segment. The stator phase winding 34 is connected to a bridge circuit of four FETs. It should be appreciated that any known electronic switching element may be used to direct the drive current through the stator winding 34 in the appropriate direction, such as a bipolar transistor. FET53 and FET55 connected in series are connected to the power supply, as are FET54 and FET56. The stator winding 34 is connected between the connection nodes of the two series FET circuits. The gate driver 46 provides trigger signals to the gate terminals of the FETs in response to control signals received from the sequence controller 44 . FETs 53 and 56 are triggered simultaneously causing the motor current to flow in the same direction. To cause the motor current to flow in opposite directions, FETs 54 and 55 are activated simultaneously. Optionally, the gate driver 46 can also be incorporated into the sequence controller 44 .

The electric machine of the invention is suitable, for example, for driving the wheels of automobiles, motorcycles, bicycles or the like. Figure 4 is a cross-sectional view of the structure of the electric motor housed in the wheel, the stator fixed rigidly on the fixed shaft and around which the rotor driving the wheel is located. The motor 10 includes an annular permanent magnet rotor 20, and a radial air gap is spaced between the permanent magnet rotor and the stator. The rotor and the stator are arranged coaxially about a rotating shaft which is the center of the fixed shaft. The stator comprises a plurality of ferromagnetically isolated elements or stator groups. The core segments 32, made of magnetically permeable material and spaced apart from each other in direct contact, have winding portions 34 formed individually on each pole. In this embodiment, seven stator groups are shown, each group comprising two protruding electromagnetic poles distributed circumferentially along the air gap. The rotor includes a plurality of permanent magnets 22 distributed circumferentially along the air gap and fixed on an annular back plate 24 . A more detailed discussion of motors employing this configuration can be found in the above-discussed Maslov et al. application 09/966102. It should be understood, however, that the vehicle in this context is merely illustrative of the many specific applications in which the electric machine of the present invention may be employed. The principles of the invention, described in detail below, can also be applied to other permanent magnet machine constructions, including a one-piece stator core supporting all phase windings.

In the example of a vehicle propulsion application, one of the user inputs into the controller is the desired torque indicated by the user's throttle command. An increase in throttle indicates a command to accelerate, which can be achieved by increasing torque. Another external input to the control processor may include a brake signal, which is generated when the driver operates the brake pedal or handle. The processor responds by immediately stopping the motor drive or changing drive control to reduce torque and speed. A separate external parking signal can be applied for immediate response to the driver's command.

The torque tracking functionality of the control system should maintain steady-state operation for a fixed input command in the event of changes in external conditions such as changes in driving conditions, road gradient, terrain, etc. The control system should be able to precisely and smoothly adapt to changes in the torque command in response to the driver's throttle input.

The control voltage V _i (t) at the output of the controller 44 represents the calculated required voltage value to obtain the torque requested by the user. Since the control voltage V _i (t) is provided by a DC power supply, the maximum value of the control voltage is limited by the maximum voltage of the DC power supply. If the calculated required control voltage to achieve the user requested torque is higher than the maximum supply voltage, a phase lead control technique is used to maximize the motor output torque. As an alternative to specifying that the sinusoidal phase current is in phase with the back EMF, as is conventionally done, the phase angle of the phase current is deliberately advanced with respect to the back EMF by a phase lead angle to maximize the output torque.

The graph in FIG. 5 shows the torque speed characteristics of the electric machine 10 with and without a phase lead angle. Curve 1 represents the maximum torque value obtained running at different speeds with no phase lead of the phase current. This curve defines the basic motor speed trajectory. Any operating point on the upper right side of this curve cannot be obtained unless a phase advance is introduced.

Curve 2 represents the maximum torque values obtained running at different speeds with a properly chosen phase lead angle. It can be clearly seen in Figure 5 that the operating range of the motor has been extended beyond the base speed indeed.

The phase advance technique is shown in Figure 6 in the form of a circular geometry. The shaded circle 1 represents the resulting current operating range for a given speed, which is limited by the finite DC supply voltage. The smaller circle 2 represents the current operating range limited by the maximum rated current I _max of the motor. The actual steady state current can occur in the region where the two circles overlap.

The value of the leading phase angle α _max , represented in Fig. 6 by the angle between the current vector and the Q axis, corresponds to the phase leading angle that provides the maximum torque T _max with respect to the projection of the current vector on the Q axis Proportional, where this current vector is as long as the radius of the circle 2, the Q axis is formed along the direction of the back EMF.

Figure 7 is a block diagram illustrating a torque controller employing a feed-forward compensation expression that takes into account measured motor operating conditions as well as individual circuit parameter values to achieve these goals. For accurate torque tracking, the desired current trajectory for each phase can be chosen according to the following expression:

I _di (t)＝I _opti sin(N _r θ _i +α _opti )

where I _di represents the current trajectory required for each phase, I _opti represents the optimal current amplitude of each phase, N _r represents the number of permanent magnet pole pairs, θ _i represents the relative position deviation between the i-th phase winding and the rotor reference point shift, α _opti represents the optimal phase lead angle of each phase.

To find the required phase currents, the following per-phase voltage control expressions are applied to the drivers of the phase windings:

V _i (t)＝L _i dI _di /dt+R _i I _i +E _i +k _s e _i

Figure 7 depicts this method, indicated at 60, by which the controller derives the voltage expression in real time using the torque command input and the signals received from the phase current sensors, position sensors and speed detectors various. The external user request (required) torque command _Tcmd corresponding to the accelerator is input into the phase lead angle optimization unit 61, and the phase lead angle optimization unit 61 determines the optimal phase angle lead angle α of each phase adopted by the control function unit 62 _opti and the optimal phase current amplitude I _opti of each phase, the control function unit 62 will use these two values to determine the current I _di (t) of each phase. This phase current is needed so that the motor can obtain the corresponding torque command T The user of _cmd requests torque. Also, the motor speed ω(t) sent from the speed approximator 50 is supplied to the phase advance angle optimization unit 61 . As will be discussed in more detail below, the phase lead optimization unit 61 may be implemented using a two-dimensional look-up table located in the controller 44 to determine for each controller principle 60, i.e. for each ^ith phase of the multiphase motor 10, The optimal phase lead angle α _opti and the optimal phase current amplitude I _opti of each phase.

The rotor position θ is input into the controller function unit 64, which generates an excitation angle θ based on the rotor position, the number of permanent magnet pole pairs (N _r ), the number of stator phases (N _s ), and the phase delay of a particular phase. The output of _i (t). The output of the controller function unit 64 is applied to the controller function unit 62 . Thus, using the field angle input thus received, the controller function unit 62 can determine the per-phase current I _di (t) required to enable the motor to determine the user requested torque corresponding to the torque command T _cmd as follows.

I _di (t)＝I _opti sin(N _r θ _i +α _opti )

The control function unit 66 calculates the difference between the required phase current I _di (t) received from the unit 62 and the measured phase current I _i (t) to output a phase current tracking error signal e _i( ( t). This error signal is multiplied by the gain factor _k in the controller function unit 68. The effect of the current feedback gain is to increase the stability of the overall system by suppressing system disturbances caused by measurement noise and any model parameter inaccuracies The output of the unit 68 is applied to the controller function unit 70. The unit 70 outputs the time-varying voltage signal V _i (t) to the gate driver 46 for selectively controlling the excitation of the phase winding 34. V _i (t ) has components that compensate for inductive effects, induced back EMF and resistance.

In order to compensate the inductance existing in the phase winding, the term L _i dI _di /dt is input into the controller function unit 70 to be added to the calculation formula of the phase voltage, where dI _di /dt represents the required phase current I _di (t) The standard time derivative of . The determination of L _i dI _di /dt is performed in the controller function unit 72 from the received α _opti , I _opti , θ _i (t) and ω(t) inputs. Unit 72 determines L _i dI _di /dt = I _opti L _i N _r ωcos(N _r θ _i +α _opti ).

To compensate for the induced back EMF voltage, the term E _i is added to the phase voltage calculation as an input from the controller function unit 74 to the function unit 70 . The back EMF compensation value is derived from the rotor angle and speed, unit 74 uses the back EMF coefficient K _ei as input. To compensate for voltage drops caused by phase winding resistances and parasitic resistances, the term R _i I _i (t) is added to the phase voltage calculation as an input from controller function unit 76 to function unit 70 .

Fig. 8 is a block diagram of a phase lead angle optimization unit 61, which can determine the optimal phase lead angle α _opti and the optimal phase current amplitude I _opti for each phase used to determine the current I _di (t) of each phase, The per-phase current I _di (t) enables the motor to obtain the user requested torque T _cmd . The phase lead angle optimization unit 61 includes a first optimization part 82 for maximizing the output torque and a second optimization part 84 for minimizing the phase current.

The first optimization part 82 determines the maximum torque output T _max at the current speed ω as an input signal from the speed approximator 50 . Under the constraints of the motor's maximum rated current _Imax and the DC supply voltage _Vc , the optimization part 82 can maximize the torque output corresponding to a given speed. Expressed mathematically by the following formula:

Maximize torque $\stackrel{\&OverBar;}{T}=\frac{1}{2}\underset{i=1}{\overset{N_{\mathrm{the\; s}}}{\mathrm{\&Sigma;}}}{K}_{\mathrm{\&tau;},i}{I}_i\cos a_i---\left(1\right)$ The following are the conditions

(R _i ² +X _{s, i} ² )I _i ² -2E _i X _{s, i} I _i sinα _i +2E _i R _i I _i xcosα _i +E _i ² ≤V _c ² (2)

and,

I _i ≤ I _max (3)

I=1, 2, ..., N _s

Among them, α _i represents the phase advance angle

X _{s, I} = L _i N _r ω is the reactance of the winding

I _max is the rated current of the motor

During each control cycle, controller 44 obtains a rotor position signal from position sensor 47 . The magnitude and phase of the back EMF are then determined assuming a sinusoidal magnetic flux distributed in the air gap. These parameters are input to the first optimization section 82, together with the speed ω, to determine the achievable maximum torque T _max (ω) at the current speed ω according to equations (1)-(3). The determined maximum torque T _max (ω) value is input into the second optimization section 84 together with the user requested torque command T _cmd .

FIG. 9 shows the curves of phase lead angle, phase current and torque output at a given speed, as a result of the optimization process performed by the first optimization section 82 . Because the motor parameters are phase-dependent values, the optimization is done individually for each single phase.

As shown in Fig. 9, the entire speed range can be divided into three regions, each of which has distinct characteristics. In the low speed area (ie below 120rpm), the limited rated current is the dominant factor to limit the torque output. The optimal phase lead angle is zero, and the phase current is equal to the maximum allowable current.

In the medium speed region (ie between 120rpm and 220rpm), the limitation of maximum current and DC supply voltage plays a major role. Therefore, a positive phase lead is necessary to maximize torque. At the same time, the phase current is still equal to the maximum allowable current. The torque output decreases as speed increases, while the optimal phase lead angle increases as speed increases.

In the high speed region (ie over 220rpm), the DC supply voltage becomes the main limiting factor. The maximum torque output continues to decrease with speed, and the phase lead continues to increase with speed. However, the phase current is lower than the maximum allowable current.

The first optimization process can be performed under various rated currents to form a family of curves corresponding to the optimal phase lead angle, phase current and torque output. Fig. 10 shows a family of curves representing phase lead angle, phase current and torque obtained at rated currents 10A and 15A corresponding to a given speed.

The maximum torque value T _max (ω) determined by the first optimization section 82 is supplied to the second optimization section 84 together with the user requested torque command T _cmd representing the required torque. Based on these parameters, the second optimization part can determine the optimal magnitude and optimum phase current Ii for a given user requested torque command T _cmd by minimizing the phase current Ii corresponding to a specific speed and required torque. The phase lead angle is as follows:

minimize current $I_i=\frac{2\min (T_{\mathrm{cmd}},T_{\max }\left(\mathrm{\&omega;}\right))}{N_{\mathrm{the\; s}}{K}_{\mathrm{\&tau;},i}\cos \left(a_i\right)}---\left(4\right)$ The following is the condition 4(R _i ² +X _{s, i} ² )T _cmd ² +4E _i N _s K _{τ, i} T _cmd (-X _{s, i} sinα _i cosα _i +R _i cos ² α _i )+( E _i ² -V _c ² )N _s ² K _{τ, i} ² cos ² α _i ≤0

This is equivalent to minimizing the phase advance angle. As a result, efficiency is maximized at this current speed and required torque.

Therefore, the second optimization section 84 determines the optimum values of the phase current amplitude and the phase lead angle according to expressions (4) and (5).

Figures 11 and 12 show the results of the optimization process for a given torque command T _cmd at two speeds of 200 and 250 RPMs, respectively. Similar to FIG. 9 , the range of the user requested torque command T _cmd in FIG. 11 can be divided into three regions. For low torques (below 28Nm), the requested torque can be achieved with zero phase lead. It is also possible to use a combination of positive phase lead and higher current to achieve the same torque at a lower efficiency. In the middle region (between 28 and 56Nm), a positive phase lead angle can be used to achieve the requested torque. It is also possible to use a combination of larger phase lead angle and higher current to achieve the same torque with lower efficiency. In the high torque region (over 56Nm), the requested torque cannot be achieved. With the optimization process performed by the first optimization section 82, the maximum attainable torque can be obtained.

According to the embodiment of the present invention, in order to support real-time motor control, the phase lead angle optimization unit 61 works according to the two-dimensional look-up table input corresponding to the motor speed and user requested torque command to provide the optimal phase current amplitude and the optimal Phase advance angle. Since the phase current optimal magnitude and optimal phase lead angle are determined based on phase-dependent parameters such as phase winding reactance, torque coefficient, and back EMF, the optimization performed by the first and second optimization sections 82 and 84 An optimization process can be performed for each phase to determine the control signal V _i (t) of the respective phase winding. As a result, the phase lead angle optimization process of the present invention can account for parametric variations in individual phase winding and stator phase component configurations.

During operation, the controller 44 continuously outputs control signals V _i (t) to the gate drivers for individual excitation of the respective phase windings. The gate drivers trigger the individual switching devices so that the order in which the windings are selected corresponds to the order established in the controller. Each successive control signal V _i (t) is related to the specific current measured in the corresponding phase winding, the instantaneously measured rotor position and speed, and also related to the model parameters K _ei and K _τi , K _ei and K _τi have been Scheduled for each phase. Therefore, for each derived control signal V _i (t), in addition to receiving the timely detected motor feedback signal, the controller must access the corresponding phase-specific parameters of the control signal. The controller thus has the ability to compensate for the respective phase characteristic differences between the different stator phases. In order to prevent overcompensation/undercompensation beyond the voltage control procedure, the adopted circuit parameters of each phase exactly match their actual values.

The per-phase torque coefficient K _τi can obtain the per-phase torque component of each phase. This parameter is proportional to the ratio between the effective torque produced and the current supplied to that phase. The torque improved by the phase is a function of the flux density that is improved with the core material of the phase, which yields the effective air gap flux density. To maximize material induction without saturating the core, the electromagnet core geometry is designed taking into account the current density as a function of the number of ampere-turns on each core section. This contradiction is even more pronounced if the motor is constructed with separate, ferromagnetically independent electromagnet cores. Changes to the winding and inductance also help determine the torque coefficient and back EMF coefficient parameters. If air pockets form in the windings, this weakens the effective magnetic flux created in the core. While a higher bundling factor can be achieved with a uniform winding, there will be variances in the wire manufacturing process. Therefore, if the controller uses the rated motor torque coefficient and the rated back EMF coefficient, the change in the phase characteristics will cause the change in the overall output torque of the motor. The torque controller method shown in Figure 7 avoids such problems by providing a predetermined per-phase torque coefficient and back EMF coefficient for each phase.

The calculations shown in Figure 7 are performed continuously in real time. The expression shown in unit 62 is chosen to provide the required current for tracking torque in the preferred embodiment. This expression can be modified if factors other than the exact tracking change in torque input command are also important. For example, in some motor applications, the degree of acceleration and deceleration is considered to avoid unnecessary adverse operating conditions. The expression in unit 62 can therefore be changed to accommodate additional considerations.

The controller method shown in Figure 7 can be implemented in an integrated implementation in which each generated control voltage output is replaced with a specific phase parameter. Alternatively, the controller 44 may provide a separate control loop for each stator phase, as shown in the partial block diagram of FIG. 13 . For each N _s motor phase, a corresponding control loop 60 _i is provided. Each loop contains the relevant parameters for the respective motor phase. Depending on the proper excitation sequence of the motor phases, this control loop can be made to work only by sensing the motor feedback signal for generating the control voltage.

In the disclosure, only a preferred embodiment of the invention and only a few examples of its generality have been illustrated and described. It should be understood that the present invention is capable of various combinations and applications and that the invention is capable of changes and modifications within the scope of the inventive principles set forth herein. For example, in the control scheme shown in FIG. 7 , the required per-phase current I _di (t) can be determined in real time from the received input T _cmd , θ _i (t) by referring to values stored in a look-up table . A lookup table will be provided for each stator phase. Optionally, optimization can be performed in real time according to expressions (1)-(5), or an optimization system such as an artificial neural network can be used to obtain optimal control parameters.

Happily, the electric machine of the present invention has a wide range of applications beyond vehicle drive. While it is preferred that the application be in a vehicle drive where a rotor surrounds a stator, advantages may also be found in other applications where a stator surrounds a rotor. Therefore, within the contemplated scope of the present invention, each inner ring and outer ring member may include a stator or a rotor, and may also include an electromagnet set or a permanent magnet set.

Although the present invention only discloses an example of a separate magnetic circuit for each electrical phase of the electric machine, the present invention can be applied to other electric machine assemblies, such as electric machines containing a common magnetic circuit. It is therefore to be understood that the present invention is capable of changes and modifications within the scope of the inventive concept expressed herein.

Claims (23)

1. the control system of a polyphase machine, this motor comprises a plurality of stator phase component and rotor, and each stator phase component comprises the phase winding that is formed on the iron-core element, and described system comprises:

Controller is used to produce control signal and encourages phase winding, comprising:

Current value is determined mechanism, be used for determining the phase current of a leading phase advance angle of back electromotive force on the phase place value and

Phase place is optimized mechanism in advance, is used to produce optimum phase advance angle value, so that motor output torque maximizes, phase current minimizes.

2. according to the control system of claim 1, the structure that wherein said phase place is optimized mechanism's configuration in advance can be optimized the phase advance angle of the every phase of motor.

3. according to the control system of claim 2, wherein said controller has the independent control ring of corresponding each stator phase, and each phase ring structure has adopted the phase advance angle optimal value of corresponding concrete phase, to produce the control signal of corresponding each phase winding.

4. according to the control system of claim 1, wherein the iron-core element of each stator phase component comprises the stator electromagnet of ferromagnetic isolation, and this electromagnetic core element is separated from each other and not directly contact, and phase winding is formed on each iron-core element.

5. according to the control system of claim 1, wherein said phase place is optimized mechanism in advance and is comprised that first optimizes part, is used for determining the maximum torque value of corresponding given speed.

6. according to the control system of claim 5, wherein said phase place is optimized mechanism in advance and is comprised that also second optimizes part, and it produces the phase advance angle optimal value in response to maximum torque value.

7. according to the control system of claim 6, wherein said second optimizes the optimum amplitude that part also produces this phase current.

8. according to the control system of claim 7, wherein said second Optimization Dept. divides to be configured to make corresponding to given speed and user asks the phase current of torque to minimize.

9. the control system of a polyphase machine comprises:

The control Voltage Calculator can be determined the phase winding of required control voltage with exciting electric in order to obtain required torque,

The electric current calculator is used for determining every phase current of the required torque of expression, this every phase current can be on phase place with respect to the super previous phase advance angle of inverse electromotive force and

Phase place is determined mechanism in advance, and it determines the value of the phase advance angle of every phase in response to the torque instruction signal corresponding with required torque.

10. according to the control system of claim 9, wherein the definite in advance mechanism of this phase place is configured to can make corresponding to the motor output torque maximization of given required torque, every phase current and minimizes.

11. according to the control system of claim 9, wherein this phase advance angle is based on that the parameter that depends on phase determines.

12. according to the control system of claim 11, wherein this depends on that the parameter of phase comprises the moment coefficient that depends on phase.

13. according to the control system of claim 11, wherein this depends on that the parameter of phase comprises with each is associated and depends on mutually back electromotive force.

14. according to the control system of claim 11, wherein this depends on that the parameter of phase comprises the phase winding reactance.

15. the method that polyphase machine is controlled in real time, this motor has a plurality of stator phase windings, and each winding is formed on the iron-core element, also has rotor, and the step that this method comprises is:

Import the torque instruction signal of a required torque of expression,

Determine to reach the required phase current of required torque,

According to this phase current, determine to encourage the required control voltage of each winding in order to obtain this required torque,

If the supply voltage that required control voltage surpasses, the phase place that makes phase current so be with respect to the super previous phase advance angle of back electromotive force,

According to required torque, determine phase advance angle that this is optimum so that output torque maximization, the phase current of motor minimize.

16. according to the method for claim 15, wherein this phase advance angle with respect to motor each be optimum mutually.

17. according to the method for claim 15, wherein the step of You Huaing comprises first optimization step, this step is to determine maximum torque value corresponding to given speed.

18. according to the method for claim 17, wherein this optimization step also comprises second optimization step, this step is in response to the optimal value that this maximum torque value produces phase advance angle.

19. according to the method for claim 18, wherein second optimization step also comprises the optimum amplitude that produces phase current.

20. according to the method for claim 16, wherein this phase advance angle is according to depending on that the parameter of phase is optimized.

21. according to the method for claim 20, wherein this depends on that the parameter of phase comprises the moment coefficient that depends on phase.

22. according to the method for claim 20, wherein this depends on that the parameter of phase comprises with each is associated and depends on mutually back electromotive force.

23. according to the method for claim 20, wherein this depends on that the parameter of phase comprises the phase winding reactance.

Images